This disclosure relates to a gas turbine engine having a case, for example, for a compressor section of the engine. More particularly, the disclosure relates to controlling the radial position of a structure supported by the case during thermal transients.
Multiple fixed and rotatable stages are arranged within the case of the engine's static structure. Typically, supported structure, such as stators and blade outer air seals, are fastened to the case. Radial clearances must be provided between the stators, blade outer air seals and adjacent sealing structure of rotating structure, such as rotors and blades. Since the supported structure and case are in close proximity to and affixed relative to one another, the supported structure thermally responds to the bulk case temperature. Thus, during temperature transients the supported structure may move radially inward more than desired, which may cause a rub event.
To avoid rub events, the designed radial clearances between the static and rotating structure are enlarged. During generally steady-state temperatures, the clearances are larger than necessary, which reduces the efficiency of the stage during cruise conditions, for example.